1. Field of the Invention
The present invention relates to a duplex automatic document feeder employed inside the image forming apparatus such as a copying machine.
2. Description of the Related Art
The conventional technology relates to the duplex automatic document feeder employed in an image forming apparatus, such as a facsimile apparatus, a copying machine, a scanner, a printer and a composite machine which includes at least two of the functions of the former. Regarding the both-sides image reading operation, the uppermost document of the document with image data on both-sides stacked on the document stacking tray is distributed to the platen located in the document feeding path. An image reading unit is located in the lower part of the platen, and the data on the first side of the document, which is facing upward when set on the document stacking tray, is read. The document is fed to the discharging roller employed in the document discharging port on the document discharging tray, and reverses the rotating direction when the lower end of the document has been fed to the discharging roller. The document is fed to the image reading unit again via the inverting path, and the second side of the document which is facing downward when set on the document stacking tray, is read.
Furthermore, when the lower end of the document has been fed to the discharging roller, the feeding direction of the document is reversed, the document is fed to the platen via the inverting path again, and without being read by the image reading unit, is discharged to the document discharging tray. Therefore, the document is stacked on the document discharging tray in the same page order as how it was when it was set in the document stacking tray.
However, after the reading operation of the both-sides of the document is completed, the document is fed to the image reading unit via the inverting path to arrange the document into the same page order as how it was when it was stacked on the document feeding tray. The document is not read by the image reading unit and is passed on, and is discharged from the document discharging port to the document-discharging tray employed in the lower position to the document discharging port. The document was fed again from this discharging tray to the document feeding path employing the image reading unit.
When the document is fed through the document feeding path which employs the image reading unit, without being read, the next document to be read cannot be taken in to the document feeding path from the document feeding tray. Thus, the speed of the reading operation of the both-sides of the document cannot be improved.